Makefile How to correctly include header file and its directory

Question

I have the following makefile   CC g   INC DIR      StdCUtil CFLAGS -c -Wall -I  INC DIR  DEPS   split h  all  Lock o DBC o Trace o    o    cpp   DEPS        CC  -o      lt    CFLAGS   clean      rm -rf  o all   This makefile and all three source files Lock cpp  DBC cpp  Trace cpp are located in the current directory called Core  One of the source file Trace cpp contains a line that includes a header file outside the current directory     in Trace cpp  include  StdCUtil split h    The header file split h is located at one level above the current directory and then in the subdirectory called StdCUtil  So that s why I added INC DIR      StdCUtil in the makefile  The overall directory structure looks like the following   root       Core                        Makefile              DBC cpp              Lock cpp              Trace cpp           StdCUtil             split h   But when I make it  it gives me the error   Trace cpp 8 28  fatal error  StdCUtil split h  No such file or directory   include  StdCUtil split h                                compilation terminated   lt builtin gt   recipe for target  Trace o  failed   Why this doesn t find the header file split h even if I specify the INC DIR in the makefile  How to correct this

User · Answer

This is not a question about make  it is a question about the semantic of the  include directive   The problem is  that there is no file at the path     StdCUtil StdCUtil split h   This is the path that results when the compiler combines the include path     StdCUtil  with the relative path from the  include directive  StdCUtil split h    To fix this  just use -I   instead of -I   StdCUtil

User · Answer

Try INC DIR        StdCUtil     Then  set CCFLAGS -c -Wall   addprefix -I   INC DIR    EDIT  Also  modify your  include to be  include  lt StdCUtil split h gt  so that the compiler knows to use -I rather than local path of the  cpp using the  include

User · Answer

These lines in your makefile   INC DIR      StdCUtil CFLAGS -c -Wall -I  INC DIR  DEPS   split h   and this line in your  cpp file    include  StdCUtil split h    are in conflict   With your makefile in your source directory and with that -I option you should be using  include  split h  in your source file  and your dependency should be    StdCUtil split h   Another option   INC DIR      StdCUtil CFLAGS -c -Wall -I  INC DIR        Ugly  DEPS     INC DIR  split h   With this your  include directive would remain as  include  StdCUtil split h    Yet another option is to place your makefile in the parent directory   root        Makefile           Core              DBC cpp              Lock cpp              Trace cpp           StdCUtil             split h   With this layout it is common to put the object files  and possibly the executable  in a subdirectory that is parallel to your Core and StdCUtil directories  Object  for example  With this  your makefile becomes   INC DIR   StdCUtil SRC DIR   Core OBJ DIR   Object CFLAGS    -c -Wall -I  SRCS     SRC DIR  Lock cpp   SRC DIR  DBC cpp   SRC DIR  Trace cpp OBJS     OBJ DIR  Lock o   OBJ DIR  DBC o   OBJ DIR  Trace o   Note  The above will soon get unwieldy    The wildcard and patsubt commands will come to your rescue   DEPS     INC DIR  split h   Note  The above will soon get unwieldy    You will soon want to use an automatic dependency generator    all    OBJS     OBJ DIR    o    SRC DIR    cpp     CC    CFLAGS  -c   lt  -o       OBJ DIR  Trace o    DEPS

User · Answer

The preprocessor is looking for StdCUtil split h in       i e   root Core   the directory that contains the  include statement   So      StdCUtil split h     StdCUtil split h and the file is missing   and in    INC DIR  i e     StdCUtil     root Core    StdCUtil     root StdCUtil    So    StdCUtil    StdCUtil split h      StdCUtil StdCUtil split h and the file is missing   You can fix the error changing the  INC DIR variable  best solution     INC DIR         or the include directive    include  split h    but in this way you lost the  path syntax  that makes it very clear what namespace or module the header file belongs to   Reference    C    include semantics   EDIT UPDATE  It should also be  CXX   g   CXXFLAGS   -c -Wall -I  INC DIR          o    cpp   DEPS        CXX  -o      lt    CXXFLAGS

[c++] Makefile: How to correctly include header file and its directory?

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